Government officials say preliminary information suggests the fire was an act of sabotage.

The government has opened two inquiries.

Police say the supervisors told panicked workers at the Tazreen Fashion factory that the fire on Saturday night was just a drill and they had nothing to worry about.

"All three are mid-level managers of Tazreen. Survivors told us they did not allow the workers to escape the fire, saying it was a routine fire drill," city police chief Habibur Rahman told AFP news agency.

Analysis

Image copyrightAFP

According to their website, Tazreen produced for a host of well-known brand names from Europe and the US.

Campaigners allege Western firms making clothes in Bangladesh hide behind inadequate safety audits to help drive down costs.

The Clean Clothes Campaign (CCC), an Amsterdam-based textile rights group, says international brands have shown negligence in failing to address the safety issues highlighted by previous fires, and that this leaves them with responsibility for yet another tragic loss of life.

The big brands say they have been working with their Bangladeshi partners to improve standards.

Around 700 garment workers have been killed in dozens of fires since 2006, according to CCC, but none of the owners has been prosecuted over previous blazes.

Questions are being asked again about how robust international brands are in policing health and safety regulations in the factories they have supply contracts with, correspondents say.

Often, a complex system of subcontractors makes policing standards either difficult or impossible, which has allowed unscrupulous operators to make savings in the areas of health and safety, they say.

"There are also allegations that they even padlocked doors," he added.

On Wednesday, police fired rubber bullets and tear gas to disperse thousands of workers in the Ashulia industrial area, just outside the Bangladeshi capital.

"We were forced to react as they started pelting officers with stones," local police official Moktar Hossain said.

The BBC's Anbarasan Ethirajan in Dhaka says there has been growing public anger over the fire, and the industrial suburbs around the capital are tense.